The invention relates to a consumer system for lifting and supporting an object i.e. a corner of an automobile; particularly to a robust consumer jack, and also to a robust two part jacking system including a power unit that can be used to place and elevate a jack stand, and further to a three-stage jack stand. The inventor of the present invention is a pioneer of the two part jacking system holding numerous issued patents for a two part jacking system and related processes, some of which are described below.
Briefly, the commercial two part jacking system consists of a power unit and a set of separate mechanical jack stands. Examples of the two part jacking system and mobile power unit are described in detail in U.S. Pat. No. Re. 32,715 and U.S. Pat. No. 4,589,630. Some examples of the jack stands are described in detail in U.S. Pat. No. 4,553,772; U.S. Pat. No. 4,490,264; U.S. Pat. No. 5,110,089; U.S. Pat. No. 5,183,235 and U.S. Pat. No. 5,379,974. The stands are capable of being vertically extended and retracted from the garage floor or road surface and, when extended, can be locked in place at any desired position by a ratchet and pawl assembly. The commercial power unit has a wheeled mobile chassis adapted to carry a plurality of the jack stands, and has a pair of lift arms adapted to mate with the outermost jack stand for placement and removal.
In use, the commercial mobile power unit is operated from its handle. It is maneuvered under a vehicle to place a jack stand in a desired location for lifting and supporting the vehicle. The power unit is activated from the handle, and the jack stand is then extended vertically to the desired height, thus lifting the vehicle on the stand. By operating the controls at the end of the handle, the operator can cause the power unit to disengage from the stand, and the stand will remain locked in its extended supporting position under the vehicle.
After the stand is raised and locked in place supporting the vehicle, or other load, in an elevated position, the power unit lift arms are lowered and the power unit is disengaged from the stand and pulled away, leaving the stand in position supporting the load. Another jack stand, carried within the chassis, is automatically transferred to the forward end the chassis for placement at another desired location of the vehicle or for use in lifting and supporting another vehicle.
To lower the vehicle and remove the stand, the power unit is maneuvered to re-engage with the stand. The engagement causes any existing jack stands carried within the chassis to be automatically transferred rearward within the chassis. By manually operating a control at the end of the handle, the operator can cause the power unit to re-engage with the stand, and to disengage the ratchet locking mechanism of the stand, and to lower the stand to its original position. The power unit remains engaged with the stand and can be pulled away from the vehicle with the stand carried within the chassis.
The original commercial power units were adapted to carry up to four jack stands within the chassis. Additional jack stands could be acquired and arranged at various stations on the garage floor to reload the power unit, so that a single power unit could be utilized to efficiently place and actuate numerous jack stands. It was found that many commercial users would utilize all of their available jack stands, and the power unit was thereafter useless until another jack stand was available to be extracted and reused. The present inventor developed a slide forward bridge that adapted the power unit to function as a load-lifting jack to more fully utilize the power unit. This invention is illustrated in U.S. Pat. No. 6,779,780 entitled Lift Bridge For Use With a Power Unit and a Load Lifting Jack, along with several other patents related to additional features of the lifting system.
Most of the prior art lifting devices, including those of the present inventor, were very rugged “commercial quality” products involving many castings and machined parts that require welding for fabrication and assembly and were very expensive to produce and market. The present inventor then developed and patented the innovative jack systems in a low cost “consumer quality” configuration that involved minimal welding and machining during fabrication and assembly. These inventions are illustrated in U.S. Pat. No. 6,565,068 entitled Economical Lifting device-Power Unit; U.S. Pat. No. 6,601,827 entitled Economical Lifting Device-Trunk Jack; and U.S. Pat. No. 6,691,983 entitled Economical Lifting Device-Jack Stand.
In the process of fully developing these consumer lifting devices, several design challenges were discovered that led to more improved, innovative components and assembles of the present invention, and more robust designs and manufacturing processes, resulting in improved performance and extended life for the user.
One such design challenge was that the original lift arms of the power unit had an extruded cylindrical recessed channel in the upper surface for retaining a compression spring for advancing the bridge. The design of the lift arm was very difficult to manufacture, had a high scrap rate and was not robust to produce. The assembly of the compression spring into the recessed channel was also difficult, and the assembly was not reliable and could sometimes malfunction.
Another such design challenge was that the original configuration of the slide-forward bridge had complex recessed channels, was difficult to produce, and was difficult to assemble with the compression spring onto the lift arms. The bridge could sometimes interfere with the jack stand or leveling pads, and was not as smooth in operation as desired.
Another such design challenge was that the two-stage jack stand was somewhat limited in range of elevation, and that a three-stage jack stand would be more compact and yet have increased elevation, and would be very desirable.
In view of the foregoing design challenges and desirable features of a two part lift and supporting system, it is an object of the present inventions to provide a consumer power unit having components that are robust to manufacture and assemble.
It is another object to provide an automatic-slide-forward-bridge assembly having components that are robust to produce and assemble, and that are reliable and durable in use.
It is another object to provide a three-stage jack stand having components that are robust to manufacture and assemble, that has extended elevation, and is reliable and durable in use.
It is another object to provide a trunk jack having components that are robust to manufacture and assemble.